Hydrogenation with a molybdenum arsenic catalyst

ABSTRACT

A method and catalyst for reacting hydrogen with aromatic hydrocarbons, with sulfur-containing acyclic and heterocyclic compounds, and with nitrogen-containing acyclic and heterocyclic organic compounds, the catalyst being comprised essentially of supported molybdenum and arsenic in their reduced forms.

United States Patent Johnson et al.

[ 51 July 11,1972

1541 H YDROGENATION WITH A MOLYBDENUM ARSENIC CATALYST |72| Inventors: Marvin M. Johnson; Donald C. Tabler,

both of Bartlcsville, Okla.

[731 Assignee: Phillips Petroleum Company [22] Filed: April 2, 1970 [21] Appl. No.: 25,239

[52] US. Cl .108/143, 208/216, 208/254, 208/264, 252/465, 252/467 [51] Int. Cl r.Cl0g 23/02 [58] Field of Search 208/143, 264, 216, 254; 260/667 [56] References Cited UNITED STATES PATENTS 2,554,597 5/1951 Stamesetal. ..208/l43 3,288,704 11/1966 OHara et a1. ..208/143 3,313,859 4/1967 Doane 208/143 3,527,695 9/1970 Lawrance et a1. .....208/142 3,159,688 12/1964 Jennings et a1 260/680 E 3,480,564 1 H1969 O'Brien et a1 ..260/680 E Primary ExaminerHerbert Levine Attorney-Young and Quigg [57] ABSTRACT 7 Claims, No Drawings I-IYDROGENATION WITH A MOLYBDENUM ARSENIC CATALYST This invention relates to reacting hydrogen with organic compounds.

In one of its more specific aspects, this invention relates to reacting hydrogen with certain materials frequently found in hydrocarbon or petroleum fractions.

In petroleum processing, a wide variety of materials, differing appreciably as to origin, are found in a single petroleum stream. For example, as a result of various processing, certain petroleum streams have been found to contain sulfur-containing organic materials I such as thiophenes and benzothiophenes, nitrogen-containing organic materials such as quinolines, and aromatics such as benzene. The elimination of such materials from such streams generally involves a plurality of steps, each affecting one or more of such materials in a manner simplifying their subsequent removal from the stock.

There has now been discovered a catalyst and a method by use of which the foregoing materials can be catalytically reacted with hydrogen, or hydrogenated, to effect their removal from the parent stream. The method and catalyst of the present invention provide for such hydrogenation.

According to the present invention, there is provided a method for hydrorefining petroleum streams which comprises contacting said stream with hydrogen and a supported catalyst comprised essentially of molybdenum and arsenic, said molybdenum and arsenic being in their reduced forms, to hydrogenate at least a portion of the hydrogenatable materials contained in said stream.

In one embodiment of this invention, when the stream contains organic sulfur-containing and/or nitrogen-containing compounds, the sulfur and/or nitrogen are converted to hydrogenated forms.

The hydrorefining can involve hydrogenation, hydrodesulfurization and hydrodenitrogenation.

When the streams contain compounds such as unsaturated hydrocarbons, including olefins and aromatics, or unsaturated sulfur-containing and/or nitrogen-containing compounds, these compounds can be hydrogenated according to the process of this invention.

Examples of the unsaturated compounds which can be hydrogenated are hexene-l, octene-l, benzene, toluene, cyclohexene, diallyl sulfide, butenyl mercaptan, thiophene, dibenzothiophene, dihydrothiophene, dihexenyl amine, decenylamine, quinoline, pyridine, 2,4-dimethylpyridine, etc.

The sulfur-containing and nitrogen-containing compounds named above can also be reacted with hydrogen in the presence of the catalyst of this invention to convert their sulfur and/or nitrogen to hydrogen sulfide and ammonia. In addition, diethyl sulfide, dibutyl amine, tetrahydrothiophene and pyridine and the like can be reacted with hydrogen to produce the corresponding saturated hydrocarbon residue after the removal of the sulfur and/or the nitrogen.

Accordingly, it is an object of this invention to provide a simplified process for hydrogenation.

It is another object of this invention to provide a simply prepared catalyst suitable for hydrogenation.

Hydrogenation of aromatic hydrocarbons, sulfur-containing acyclic and heterocyclic, and nitrogen-containing acyclic and heterocyclic compounds is a useful process as applied to various hydrocarbon streams containing these impurities encountered in the petroleum refining or petrochemical fields. This is particularly so when these materials are found in minor amounts in various feedstreams to processes in which their presence is deleterious as, for example, in contaminating catalysts, reducing yields, and the like. Accordingly, the method and catalyst of this invention find wide use in feed purification processes.

In general, the hydrorefining conditions of this invention involve a temperature of from about 250 to about 1,000 F., pressures of from about 100 psig to about 3,000 psig, a feed rate of about 0.1 to about LHSV and at an amount of hydrogen in the range of about I to about 50 moles per mole of compound to be reacted with the hydrogen.

The method of this invention employs a catalyst, comprised essentially of molybdenum and arsenic in their reduced forms. Preferably, the catalyst is supported. Alumina and activated alumina are most active, although other supports such as calcium aluminate, silica, titania, and magnesium oxide, can be used.

In general, the catalyst is prepared by impregnating the granular support with molybdenum and arsenic in the form of their water soluble compounds, the impregnation being done with each compound either separately or simultaneously. Thereafter, the impregnated support is dried in air at a temperature of about 850 to about 900 F. and reduced in a stream of hydrogen at a temperature of from about 800 to about 1,000 F.

The amount of molybdenum and arsenic with which the support is impregnated will vary, depending upon the specific hydrogenation for which the catalyst is intended.

The finished catalyst will contain from about 2 to about 20 weight percent molybdenum and will have a molybdenum to arsenic weight ratio of about 1:1 to about 5:1. In its preferred composition, the catalyst will contain from about 5 to about 10 weight percent molybdenum and will have a molybdenum to arsenic weight ratio of from about 3:1 to about 4:1 for hydrogenation of aromatics and for hydrodesulfurization and hydrodenitrogenation. For hydrogenation of heterocyclic nitrogen-containing and/or heterocyclic sulfur-containing compounds, the weight ratio of molybdenum to arsenic is from about 1.5:1 to about 25:1.

The method and catalyst of this invention are particularly suitable for the hydrogenation of benzene when present in cyclohexane in an amount of from about 2 to about 50 weight percent. For such purposes, the hydrogenation is conducted at a temperature of from about 250 to about 550 F at a pressure of from about 200 to about 1,500 psig, at a feed rate of from about 0.1 to about 10 liquid volumes per hour of feedstream per volume of catalyst (LI-ISV). Hydrogen is introduced into the reaction in an amount of from about 3 to about 15 moles per mole of benzene contained in the feedstream. Under such conditions, the benzene is hydrogenated to cyclohexane.

When employed for the hydrogenation of heterocyclic nitrogenand/or sulfur-containing compounds, the method and catalyst are particularly suitable for the conversion of compounds such as thiophene to dihydrothiophene and/or tetrahydrothiophene, particularly when present in a stream which also contains hydrocarbons in an amount from about 2 to about 50 weight percent. For such purposes, the reaction is conducted at a temperature of from about 300 to 650 F at a pressure of from about 500 to about 3,000 psig, at a feed rate of from about 0.1 to about 10 LHSV, with hydrogen being introduced into the reaction in an amount of about 1 mole per mole of thiophene when the conversion is to the dihydrothiophene and with hydrogen being introduced into the reaction in an amount of about 2 moles per mole of thiophene when the conversion is to the tetrahydrothiophene. The hydrogenated heterocyclic is generally removable from the feedstream by distillation.

When employed for hydrorefining of sulfur and/or nitrogen organic compounds, the method and catalyst of this invention generally produce gaseous sulfur-containing and nitrogencontaining compounds, such as hydrogen sulfide and ammonia, which are easily separated from the feedstream. In these hydrogenations, the reaction is generally conducted at temperatures of from about 550 to about 1000 F. at a pressure of from about to about 1,500 psig, at a feed rate of from about 0.1 to about 10 LHSV, with hydrogen being introduced into the reaction in an amount from about 0.5 to about 5 moles per mole of total feed.

In general, the aforementioned reactions can be conducted simultaneously when more than one of the hydrogenatable materials occurs in the same feedstream. However, the hydrogenation of aromatics is preferably conducted in the absence of sulfur compounds.

EXAMPLE I A catalyst comprised of weight percent molybdenum and a mole ratio of molybdenum to arsenic of about 3 to 1 was prepared using 1040 mesh particulate alumina as a support.

Five grams of H AsO were dissolved in 50 ml. water. Eighteen and five-tenths grams of (NH Mo O -4H O were added to the resulting solution. The white precipitate which formed on mixing was dissolved by adding 10 ml. of 28 percent ammonium hydroxide solution to the resulting solution to form a clear solution.

The total volume of the clear solution was slurried with 100 grams of dried alumina, the total volume of the clear solution being absorbed by the alumina. The alumina was then dried for 48 hours at room temperature and finally at 100 C. The dried alumina was heated in air at 960 F. for three hours to remove ammonia, after which the dried material was activated by heating in hydrogen at 800 F. for 3 hours. The finished catalyst contained 6.9 weight percent molybdenum and 1.9 weight percent arsenic.

EXAMPLE II A second catalyst containing about 7.5 weight percent molybdenum and about 3.3 weight percent arsenic was prepared in the manner described in Example I, employing 8.7 grams of H AsO. in 30 ml. of water with 18.5 grams (NH ),,Mobq7O -4H O and 40 ml. of 28 percent NH solutio Ninety-four grams of l0-40 mesh alumina were used.

These examples indicate methods of preparing catalysts of this invention.

EXAMPLE Ill The catalyst of Example I was employed for the hydrogenation of benzene.

A feedstream comprised of n-pentane and 15 weight per cent benzene was contacted with the catalyst and with hydrogen, the mole ratio of hydrogen to benzene being 8 to l. The catalyst was maintained at 530 to 550 F. at a pressure of 800 psig. The feedstream charge rate was 2 LHSV, being equivalent to a benzene LHSV of about 0.3. The run was conducted for a duration of seven hours. Initial conversion of the benzene to cyclohexane was 99.9 percent. Near the end of the seven hour period, the temperature of the catalyst was increased to 620 F. with the result that the conversion of benzene to cyclohexane decreased to 76 percent.

The above example indicates the effectiveness of the catalyst and method of this invention in hydrogenating aromatics.

EXAMPLE IV EXAMPLE V A feedstream was prepared consisting of 2.92 weight percent thiophene in benzene. This stream was contacted with a catalyst prepared in Example 11 under the conditions indicated below with the results noted.

Run No. l 2 3 4 Temperature, F. 557 609 589 560 Hydrogen Rate.

moles/mole Thiophene 30 30 30 30 Pressure, psig. 1000 1000 1300 1300 Feed rate, LHSV 2 2 2 2 Product analysis, wt.%

Thiophene 1.55 0.630 0.939 1.46

Tetrahydrothiophene 0.76 0.70 1.07 0845 Conversion of 47.0 78.5 68.0 50.0

Thiophene,

EXAMPLE VI To benzene was added 3.6 weight percent thiophene. This was the equivalent of a sulfur content of 1.37 weight percent. The resulting blend was then contacted with a catalyst containing 6.9 weight percent molybdenum and 1.9 weight percent arsenic supported on activated alumina which catalyst had been activated in hydrogen at 1,000 F. Operating conditions and results were as follows:

Operating Conditions Temperature, F. 670 675 Pressure, psig. 800 Hydrogen, moles/mole Thiophene 23 Feed Rate, LHSV 2 Thiophene content of product, wt. 71 After 1 hour Operation After 18 hours Operation The effluent gas was passed through cadmium sulfate solution. Yellow cadmium sulfide formed showing that H 5 was present in the effluent gas.

These data indicate the operation and continued effectiveness of the method and catalyst of this invention in hydrogenating sulfur compounds for the purpose of desulfurizing aromatic mixtures containing thiophene.

EXAMPLE VII To benzene was added 1.7 weight percent dibenzothiophene. This was the equivalent of a sulfur content of 0.30 weight percent. The resulting blend was then contacted with a catalyst comprised essentially of 6.9 weight percent molybdenum and 1.9 weight percent arsenic supported on activated alumina which had been activated in hydrogen at l,000 F. Operating conditions and results were as follows:

Operating Conditions Temperature, F. 657 Pressure, psig. 800 Hydrogen, moles/mole Dibenzothiophene Feed Rate, LHSV 2 Sulfur content of product, wt. 7: 0.03 (limit of detection) The above data illustrate employment of the catalyst and method of this invention in sulfur removal from aromatics by hydrodesulfurization.

EXAMPLE Vlll To benzene were added both sulfur-containing and nitrogen-containing compounds, sulfur being added in the from of dibenzothiophene and nitrogen being added in the form of quinoline. Dibenzothiophene was added in an amount of 1.7 weight percent to provide a mixture having 0.30 weight percent sulfur and quinoline was added in an amount of 1.7 weight percent to provide a nitrogen content of 0.18 weight percent in the mixture. A portion of the resulting stream was contacted with that catalyst (I) employed in Example VII and a portion was contacted with a catalyst (II) comprised essentially of about 7.5 weight percent molybdenum and about 3.3 weight percent arsenic on alumina, the catalyst having been activated with hydrogen at 800 F. Results were as follows:

The above data indicate the operability of the catalyst and method of this invention over a wide range of conditions. The ability of the method and catalyst of this invention to hydrogenate such compounds as are concerned in the above examples, and particularly dibenzothiophene and quinoline, is of significance in that these materials are sometimes present in petroleum fractions and are difficult to remove.

It will be seen from the above that various modifications can be made to the method and catalyst of this invention. However, such are considered as being within the scope of the invention.

What is claimed is:

l. A method for selectively hydrogenating aromatic hydrocarbons contained in a hydrocarbon feedstream which comprises contacting said feedstream with hydrogen and a catalyst consisting essentially of about 2 to about 20 weight percent molybdenum and a weight ratio of molybdenum to arsenic of about 1:1 to about 5:1 and an inorganic oxide inert support under hydrogenation conditions, said catalyst having been reduced with hydrogen prior to said contacting.

2. The method of claim 1 in which said molybdenum and arsenic are supported on a support selected from the group consisting of alumina, calcium aluminate, silica, titania and magnesium oxide.

3. The method of claim 2 in which said catalyst comprises from about 5 to about 10 weight percent molybdenum, said molybdenum and said arsenic being present in a weight ratio of about 3 to about 4.

4. The method of claim 2 in which said hydrogenation is carried out at a temperature of from about 250 F. to about l,000 F., a pressure of from about psig to about 3,000 psig, a feed rate of about 0.1 to about 10 LHSV, and employing at least a stoichiometric quantity of hydrogen.

5. The method of claim 2 in which aromatics in a hydrocarbon feedstock are selectively hydrogenated by contacting said feedstock and added hydrogen with said catalyst at a temperature ranging from about 250 to about 550F and a stoichiometric excess of hydrogen based upon aromatics in said feedstream.

6. The method of claim 2 in which benzene is contacted with said catalyst and hydrogen at a temperature of about 550 F., at a pressure of about 800 psig, and a benzene charge rate of 0.3 LHSV, said hydrogen being employed in a mole ratio of 8 to l of benzene, said catalyst being comprised of 10 weight percent molybdenum and a mole ratio of molybdenum to ar senic being about 3 to 1, said molybdenum and said arsenic being supported on alumina.

7. A method according to claim 1 wherein the aromatic hydrocarbon in said hydrocarbon feedstream is benzene. 

2. The method of claim 1 in which said molybdenum and arsenic are supported on a support selected from the group consisting of alumina, calcium aluminate, silica, titania and magnesium oxide.
 3. The method of claim 2 in which said catalyst comprises from about 5 to about 10 weight percent molybdenum, said molybdenum and said arsenic being present in a weight ratio of about 3 to about
 4. 4. The method of claim 2 in which said hydrogenation is carried out at a temperature of from about 250* F. to about 1,000* F., a pressure of from about 100 psig to about 3,000 psig, a feed rate of about 0.1 to about 10 LHSV, and employing at least a stoichiometric quantity of hydrogen.
 5. The method of claim 2 in which aromatics in a hydrocarbon feedstock are selectively hydrogenated by contacting said feedstock and added hydrogen with said catalyst at A temperature ranging from about 250* to about 550* F and a stoichiometric excess of hydrogen based upon aromatics in said feedstream.
 6. The method of claim 2 in which benzene is contacted with said catalyst and hydrogen at a temperature of about 550* F., at a pressure of about 800 psig, and a benzene charge rate of 0.3 LHSV, said hydrogen being employed in a mole ratio of 8 to 1 of benzene, said catalyst being comprised of 10 weight percent molybdenum and a mole ratio of molybdenum to arsenic being about 3 to 1, said molybdenum and said arsenic being supported on alumina.
 7. A method according to claim 1 wherein the aromatic hydrocarbon in said hydrocarbon feedstream is benzene. 